You have raised some very valid points.
No, there is no test for over washing.
I wash and test, I test to the first indication that the print passes the test and then stop. That presumably prevents overwashing.
The short answer is that you can pick either Ilford rapid method or Kodak slow method. Several other manufacturers publish instructions that are the same as or modified from either of them, and they are also ok as long as the method was well tested. Anything more than that are of academic concern, and you should certainly understand the factors involved if you have to devise your own washing technique. Most people are perfectly fine with either Ilford or Kodak method.
Originally Posted by Gary Holliday
Think about it. Anyone who does darkroom work has to wash material. Manufacturers make simple and effective instructions for their customers. Not many people have to devise their own washing technique. It is actually rather unusual that so many people at APUG read thread like this and the other ongoing one although they are not trying to make their own washing routine. If you are happy to accept existing, well tested method, you can either go with Ilford or Kodak method.
Recommendation like you referred to is still a standard method if you use acid hardening fixer. They require a lot more washing to remove the residual chemicals to the same level. But most people use non-hardening rapid fixer, which washes out very fast, especially with films and RC papers. So if you just look at the number of minutes or amount of water used, you might think Ilford method is absurdly short, and that's what some people (including yourself) are concerned. But if you understand the chemistry behind it, or if you run your own test, the concern is wiped out right away. I do test for residual thiosulfate on rather routine basis, and haven't seen a single incident that Ilford method was insufficient, even for the highest level archival standard specified in the applicable ISO standard.
It's clear that Ilford's method is fairly controversial, so practical alternatives are what I'm hoping for.
I was originally taught (many years ago) to wash in flowing water, exchanging the water regulary for 20 mins.
I use Ilford Hypam at present, so needed advice on a shorter wash time.
The price of short Ilford method is that you have to make sure your fixer is non-hardening rapid fixer. If your fixer is not of this type, you'll have to use more elaborate washing process.
First of all, "overwashing" is a rather paradoxical description.
Originally Posted by mhv
To make the story simple, I'll tell you when you have to worry about it and when you don't.
The notion of overwashing is completely irrelevant and unnecessary if (1) a pictorial camera negative film is processed; (2) your print is toned in any of the archival toners; (3) if you don't care about archivality of the print.
Overwashing can harm the image stability if you intend the untoned print for long term storage. Again, anyone who's sensible would use anyy of the archival toner for prints made for long term archive.
The notion of overwashing came from the finding that a very small amount of residual thiosulfate can sometimes protect image silver when there is no other protection (e.g., toning). However, the degree of protection provided by even the optimal amount of thiosulfate is smaller than a light toning with polysulfide or solid toning from selenium. Another problem with relying on the optimal residual thiosulfate is that it is impractical to aim the optimal value by adjusting the washing method. Therefore, anyone serious about archival printing should consider using any of the archival toning process, thereby making the notion of "overwashing" is irrelevant.
Manufacturers know that "overwashing" exists and it is counterintuitive to average darkroom workers who are not serious enough to go through the toning process. This is a very tricky issue in phrasing usage instruction, and each manufacturer thinks hard to be as "informative" and "courteous" but without making the instruction overly complicated. One example is that many manufacturers overly emphasize it is unnecessary to use more washing time than indicated. They may also emphasize that there is no need to use washing aid for RC prints as long as the fixer is fresh. They would still recommend polysulfide, selenium or gold toner if you are serious about image permanence.
Back to your original question. You can use methylene blue test or amylose iodine test described on the page linked below to test for overwashing, if you really want to do that. But as you already saw above, avoiding "overwashing" is more of prevention of wasteful effort than an effective and active means of increasing image permanence.
Described in this page:
And more generally speaking, besides the test of time and the HT-2, what tests are reliable indicators of a properly processed print?
There are other tests that are intentionally omitted in this page. Those tests are unreliable or unsuitable and are currently not recommended.
If you stick with standard processing sequence from Ilford, Kodak or mine (silvergrain), and don't deviate from the recommended usage and processing capacity, users can rest assured that their material is properly processed.
My own understanding so far would be that although there are theoretical guidelines regarding wash, mere conformity to these rules does not replace actual verification, and does not warrant by itself that a print or a film was properly processed, right? Somehow I think that people can get by with a as little theoretical knowledge as is needed to validate a bullet-proof testing.
Testing is recommended if you have reason to be concerned, such as unfamiliar processing chemicals, unfamiliar paper stock, need to limit the washing water to the minimum due to water supply situation, etc. It is also easy and simple to perform if you are very serious about archival processing.
More often on this site people recommend to test for your own as a way to end otherwise endless battles from people with strong dogma. Think about it, most Kodak users, most Ilford users, almost all other darkroom users, they never run their own tests but you don't hear about images that are deteriorated due to too much residual thiosulfate from careful darkroom workers who recognizes the importance of proper washing. This is because the majority of deterioration of image silver is due to oxidative attacks and not residual thiosulfate. Most people who are reading this thread and concerned about image permanence are actually better thinking about the toning process rather than washing process.
Last edited by Ryuji; 04-26-2007 at 11:15 PM. Click to view previous post history.
Ok, with the stuff that was asked in this and the other thread, I revised this page:
I intentionally excluded unimportant and generally irrelevant factors such as developer retention. This is more of a problem with monobath and not with conventional processing.
Will revise the page with more stuff later, but just for your information.